take out the spark plug ,take off the carb and the insulator and gasket till you see just the bare intake port. now take some dish washing soap and with your finger wipe across the small hole till you see that you have created a bubble cover now rotate the engine crankshaft in the normal direction do you get a bigger bubble? if not that gasket goo that you mentioned earlier has plugged this passage way!!!! also take some more soap and put around the crankshaft where the seals meet , turn the crank does it bubble ? if so then proceed to replace the seals and or the bearings that might be sloppy.

tom